Timeline for Can third-order arithmetic prove the consistency of second-order arithmetic?
Current License: CC BY-SA 4.0
5 events
| when toggle format | what | by | license | comment | |
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| Oct 2, 2020 at 4:58 | history | edited | John Licato | CC BY-SA 4.0 |
clarified my misunderstanding with the second part of my question, but also clarified why the first part is still unanswered.
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| Aug 6, 2019 at 13:31 | comment | added | Andreas Blass | Sorry, I should have written "the idea that $Z_1\vdash$ is equivalent to$Z_2\vdash$. | |
| Aug 6, 2019 at 12:59 | comment | added | John Licato | Sorry, but I'm confused by your comment---I didn't write $Con_{Z_2}$ anywhere, nor did I claim it was equivalent to $Con_{Z_1}$. | |
| Aug 5, 2019 at 18:12 | comment | added | Andreas Blass | Your apparent contradiction arises from conflating the slogan "second-order logic can express anything that higher-order logics can" with The idea that $\text{Con}_{Z_1}$ is equivalent to $\text{Con}_{Z_2}$. Unfortunately, I don't have time right now to write more, but I think that, if you check the theorem underlying that slogan (in particular the relevant meaning of "express"), the difficulty may disappear. | |
| Aug 5, 2019 at 15:47 | history | asked | John Licato | CC BY-SA 4.0 |